Some people have shot full power .45acp ammo in the Webley MkI and MKII service revolvers with no mishaps, but there have also been a few that have let go as shown in the pics on the previous posts.
I have seen quite a few MkI/II revolvers modified for .45acp that have been shoot loose - frame hinges and latches are sloppy. The steel in the old webley frames is soft enough that full power .45acp loads distorts them in time. It is possible to tighten up loose hinges and resurrect the old pistols but better to not go there in the first place.
The MKI/II/III webley service revolvers were designed for for the webley .455, which was/is loaded to about 12,000 psi. Factory .45acp is usually loaded to approx 17,000 - 18,000 psi. 50% overload is a bit much, I think.
IMO, you need to download the .45 acp load to .455 webley levels, which will still give decent performance - a 260 gr slug travelling at 650-700 fps is pretty effective. Lighter bullets work good in some of the old webleys and it is possible to push them faster.